Field of the Invention
The present invention relates to an engine control system.
Background
In recent years, as a technique of improving fuel consumption performance and environmental protection performance of a vehicle, the introduction of a Bi-Fuel Engine system, which selectively switches between liquid fuel such as gasoline and gas fuel such as compressed natural gas (CNG) and performs operation control of a single engine, has advanced. In general, in the operation control of an engine, an air-fuel ratio feedback control of controlling a fuel injection amount such that an actual air-fuel ratio becomes a target air-fuel ratio (theoretical air-fuel ratio) is performed. However, in the case of a Bi-Fuel Engine system, it is necessary to perform an air-fuel ratio feedback control during both the liquid fuel operation (gasoline operation) and the gas fuel operation (gas operation).
For example, Japanese Patent Application, Publication No. 2011-220253A discloses a technique of individually learning (acquiring) a correction coefficient used for the air-fuel ratio feedback control with respect to the duration of both the liquid fuel operation and the gas fuel operation in the Bi-Fuel Engine system and controlling a fuel injection amount by use of the correction coefficient stored individually when switching between the liquid fuel operation and the gas fuel operation.
Further, Japanese Patent Application, Publication No. 2011-220253A also discloses a control in which in order to remove the impact of evaporated fuel, called vapor, resulting from the evaporation of liquid fuel, purging the vapor to the engine is inhibited while the correction coefficient is being learned.